In any mobile communication system, the identification of frame boundaries and frame types are critical post-demodulation aspects of the processing performed by a superframe lock subsystem. The superframe lock subsystem must be capable of reliably acquiring, tracking and maintaining frame lock in minimal time regardless of the presence of signal fades and blockages and independent of frame type. The superframe lock subsystem must also be capable of recognizing changes in frame type, overcoming symbol slippage and extracting data as early as possible, all during poor channel conditions.
Frame alignment procedures conventionally utilize unique words embedded within the bit stream which identify frame boundaries. A frame alignment procedure generally consists of a search process and a confirmation process. Conventionally, a search process for a unique word comprises sequentially searching each bit position in each frame for a bit pattern which matches the unique word. In the presence of fades, blockages or poor channel conditions, the reproduced bit stream may be degraded. In a worst case, a search process for the unique word may comprise checking all the bit positions in each frame more than once. Accordingly, frame alignment in conventional superframe lock subsystems can be delayed appreciably. In addition to suffering from poor frame lock acquisition performance, the conventional superframe lock subsystem uses processing time uneconomically since the search process requires checking all bit positions in each frame at least once for unique words. Accordingly, a need in the art exists for a superframe lock subsystem which reliably and quickly acquires frame lock while conserving processor throughput.